1. Field of the Invention
The present invention relates to a vending machine for selling chiefly canned beverages, bottled beverages or paper-packed beverages, and more particularly to a cooling-control method adapted to cope with the peak of power demand, and a cooling control device using such a method.
2. Description of the Related Art
Excessive power demand in the summer daytime has posed a serious problem and as a link in the chain of countermeasures against such a demand, it has been examined to force the suspension of the cooling operation of vending machines for dispensing cooled canned beverages in a prescribed time zone, that is, a peak cut in the daytime in which power demand is concentrated. Since the suspension of the cooling operation accompanies a rise in the temperature of merchandise, there is the necessity of taking it into consideration to minimize the annoyance of consumers due to a rise in the temperature of merchandise while the peak of power demand is effectively dealt with. For the reason stated above, one of the steps required is to cause normal operation to be restored when the merchandise temperature has reached a predetermined upper limit even in the peak cut time zone.
A vending machine of the sort mentioned above is generally equipped with a cooling mechanism to be on-off controlled by temperature sensors and arranged so as to cool the merchandise accommodated in a merchandise housing by circulating the air cooled by the cooling mechanism through the merchandise housing and discharging articles of merchandise one after another with the forefront one first at the point of sales, the temperature sensors for controlling the cooling mechanism being normally adapted to detect the in-housing air temperature near a cooled air outlet. However, the in-housing air temperature detected by the temperature sensors covers temperatures of merchandise of more than one kind stored in a plurality of sections (hereinafter called the columns) formed in the merchandise housing for various kinds of merchandise. When only a specific column is filled with supplementary merchandise, for example, the temperature detected by the temperature sensors will not rise so much if merchandise temperatures in the other columns are low though the temperature of the supplemented merchandise is extraordinary high. In other words, the in-housing air temperature would not truly reflect the temperature of extraordinary merchandise in such a specific column. There is therefore the possibility that the peak cut is allowed to continue without the detection of the fact that the merchandise in any one of the columns has reached the upper-limit temperature during the peak cut.
The present inventors previously developed a technique for on-off controlling a cooling mechanism by tightly attaching a temperature sensor to the surface of merchandise within a housing so as to detect the merchandise temperature instantly and the present applicant also applied for a patent (Japanese Patent Unexamined Publication No. Hei 7-29057). As the temperature sensor (merchandise temperature sensor) is capable of detecting the temperature of merchandise itself, temperature control can be exerted more accurately than what has been effected by the conventional method of detecting the in-housing air temperature, and the merchandise temperature in each of the individual columns is made clearly available, so that an excessive rise in the merchandise temperature during the peak cut becomes detectable.
When the peak cut is applied, moreover, the on-off temperature of the cooling mechanism is shifted so that it is made lower than the temperature in the normal time zone for a predetermined time prior to the time zone during the peak cut; the application of the peak shift is preferred in this manner when the merchandise has been cooled down beforehand. Further, the normal operation is caused to be restored when the merchandise temperature conversely begins to become lower during the peak cut because it is necessary to prevent the merchandise from being frozen. Notwithstanding, the detection of the merchandise itself is very effective for antifreeze.
As set forth above, though control of the cooling mechanism for directly detecting the merchandise temperature is advantageous in that control accuracy is high, such a temperature sensor has to be installed in all the columns to make the most of the advantages and the problem is that this arrangement is costly. More specifically, since the in-housing air temperature includes the merchandise temperature in all the columns in the same chamber, only one temperature sensor (in-housing temperature sensor) is normally needed for a plurality of columns. However, the merchandise temperature varies with the column and consequently it is required to provide such a merchandise temperature sensor for each column to take hold of the temperature variations.
A possible method of reducing cost when the cooling mechanism is controlled by detecting the merchandise temperature is to select one or more than one column as representative ones, so that the temperature sensors are installed in only these columns. However, the partial installation of temperature sensors may result in failing to detect the insufficiently cooled condition of supplementary merchandise when the merchandise stored in a column without the temperature sensor happens to have been sold continuously, thus entertaining the fear of allowing the insufficiently cooled merchandise to be directly sold (merchandise situated close to a merchandise carry-out mechanism, that is, articles to be discharged earlier in the carry-out order are selectively cooled normally in a typical vending machine).